I bought and installed the Ford Racing kit from Summit Racing. If the kit is for a Zetec it should work, there's no actual tapping into the computer to get it to work. There's quite a few wires and switches to change out, but it pulls the speed sensor data off of the wire behind the passenger-side kick panel and all they have you do is tap the signal with a tap splice.

This is all assuming you're dealing with genuine Ford products...they might just be selling you a vaccum solenoid universal kit that works on any car.